Nanoparticles, which may include nanocrystals, nanocrystallites, nanocrystalline materials, quantum dots, and quantum dot materials, among other classifications, are produced and used for wide ranging applications. Production of homogenous nanoparticles of similar size ensures a consistency necessary for reliable and predicable use in downstream applications. Coordinating ligands bound to the surface of the nanoparticles may provide a wide variety of properties to the nanoparticles.
The properties of the nanoparticles are highly dependent on the size and composition of the particles. For example, nanocrystals are crystalline particles with at least one dimension measuring less than 100 nanometers (nm), and may comprise single-crystals or polycrystalline materials, as opposed to amorphous, non-crystalline solids. Based on their size, structure, and composition, the nanocrystals may have unique optical properties.
Some classes of nanocrystals have electrochromic properties. The electrochromic nanocrystals are able to reversibly change their optical properties responsive to a change in particle charge (oxidation or reduction). By applying an electrochemical potential to the nanocrystals, the absorption and transmission properties of the nanocrystals change. Depending on the spectral qualities of the nanocrystal, this process may result in a visible color change.
Smart windows provide an application for electrochromic nanocrystals that may both save energy and enhance privacy. Windows may be coated with nanocrystalline materials that are transparent at a default bias and charge state. However, when the nanocrystals are electrically charged and achieve a certain bias, light may be blocked. Some electrochromic nanocrystals are spectrally specific for certain wavelengths (e.g., UV, Visible, Near-IR). However, some electrochromic nanocrystals may be capable of blocking visible light at one bias, but at a different bias are transparent to visible light, but block near-IR light. By selectively layering nanocrystals onto a glass substrate (optionally including optically transparent conductive oxide nanocrystals), the transmission of a smart window may be optimized based on time of day and/or time of year, and may further be optimized for energy efficiency and/or privacy.
As a method for producing nanocrystals, methods described in U.S. Pat. Nos. 7,531,149; 8,133,441; 8,211,388; U.S. Patent Application Publication No. 2010/0269634; U.S. Patent Application Publication No. 2010/0251856; U.S. Patent Application Publication No. 2009/0258076; U.S. Patent Application Publication No. 2009/0269269; International Patent Publication No. WO2009/092684; U.S. Patent Application Publication No. 2013/0089739; U.S. Patent Application Publication No. 2015/0059236; Testino, A. et al., “Continuous Polyol Synthesis of Metal and Metal Oxide Nanoparticles Using a Segmented Flow Tubular Reactor (SFTR).” Molecules 2015, 20, pp. 10566-10581; Ragappa, D. et al., “Synthesis, characterization and organic modification of copper manganese oxide nanocrystals under supercritical water.” Journal of Supercritical Fluids 2008, 44, pp. 441-445; and Choi, C. H. et al., “Aqueous Synthesis of Tailored ZnO Nanocrystals, Nanocrystal Assemblies, and Nanostructured Films by Physical Means Enabled by a Continuous Flow Microreactor.” Crystal Growth & Design 2014, 14(9), pp. 4759-4767 are known, for example.